1. Field of the Invention
The present invention relates to a center bearing support which rotatably and elastically supports a propeller shaft of a motor vehicle to a vehicle body side via a center bearing and carries out a vibration absorption and a buffering.
2. Description of the Conventional Art
A center bearing which is installed to an outer periphery of a propeller shaft of a motor vehicle is elastically supported to a vehicle body side via a center bearing support, whereby a vibration transmission is reduced between the propeller shaft side and the vehicle body side under traveling.
As shown in FIG. 10 or FIG. 11, a center bearing support 100 of this kind is provided with an outer ring 101 which is fitted and attached to an annular bracket 110 in the vehicle body side, an inner ring 102 which is arranged in an inner periphery thereof and fitted and attached to an outer race 121 of a center bearing 120, a presser bar ring 103 which is fitted to the inner ring 102 so as to be integrated and holds the outer race 121, and an elastic body 104 which is made of a rubber-like elastic material (a rubber material or a synthetic resin material having a rubber-like elasticity), elastically coupling the outer ring 101 and the inner ring 102 and is formed as a bellow-like bent shape.
Further, among them, the center bearing support 100 shown in FIG. 10 is structured such that end portions 102a and 103a in an opposite side in an axial direction in the inner ring 102 and the presser bar ring 103 are bent to an inner diameter side so as to be opposed to an outer peripheral surface of a propeller shaft 130 via a slight gap, and oil seals 105 and 106 which are slidably brought into close contact with the outer peripheral surface of the propeller shaft 130 are installed to an inner peripheral surface of a tube portion in the vicinity of the end portions 102a and 103a in the inner ring 102 and the presser bar ring 103. Further, dust covers 107 and 108 which surround outer diameter sides of the end portions 102a and 103a of the inner ring 102 and the presser bar ring 103 are installed to the outer peripheral surface of the propeller shaft 130, whereby labyrinth seals LS1 and LS2 are formed in outer sides of the oil seals 105 and 106. Further, in accordance with the structure mentioned above, a muddy water, a dust or the like which comes flying during the traveling of the motor vehicle is prevented from making an intrusion into an inner peripheral space of the inner ring 102 and the presser bar ring 103 in which a grease (not shown) is filled and the center bearing 120 exists, for example, refer to Japanese Patent Publication No. 2008-286221.
However, since the oil seals 105 and 106 are contact type seals, a tension force thereof comes to a resistance against a rotation of the propeller shaft 130, thereby causing a loss of a driving force, that is, a deterioration of a fuel consumption. Further, since the oil seals 105 and 106 are embedded, there is a problem that a number of the parts is increased, and a cost is increased.
On the contrary, in the center bearing support 100 shown in FIG. 11, since the end portions 102b and 103b in the opposite side in the axial direction to each other in the inner ring 102 and the presser bar ring 103 are bent to the outer diameter side, and are opposed to the inner peripheral surfaces of a pair of dust covers 107 and 108 which are installed to the outer peripheral surface of the propeller shaft 130, the Labyrinth seal LS1 constructed by the zigzag bent gap is formed between the elastic body 104 and the end portion 102b of the inner ring 102, and the dust cover 107 and the outer peripheral surface of the propeller shaft 130, and the labyrinth seal LS2 constructed by the zigzag bent gap is formed between the end portion 103b of the presser bar ring 103 and the dust cover 108, and the outer peripheral surface of the propeller shaft 130. Further, in accordance with the structure mentioned above, the muddy water, the dust or the like which comes flying during the traveling of the motor vehicle is hard to make an intrusion into the inner peripheral space of the inner ring 102 and the presser bar ring 103 in which the grease (not shown) is filled and the center bearing 120 exists, for example, refer to Japanese Patent Publication No. 2001-280342.
However, in the structure in FIG. 11, a sealing performance of the labyrinth seals LS1 and LS2 is lowered, at a time of stopping, and at a time when a front wheel propeller shaft stops in the case of two-wheel drive traveling in a part-time four-wheel drive vehicle. Particularly, as shown by a broken line in the drawing, in the case that the muddy water is attached to an upper portion of a convex surface in an upper side of the propeller shaft 130 in the bellow-like bent portion of the elastic body 104, there is pointed out a problem that the muddy water falls down along the surface of the elastic body 104 so as to easily make an intrusion into the inner periphery of the inner ring 102.